Liquid fuel pump



Nov. 3, 1953 F. M. EVANS LIQUID FUEL PUMP 2 Sheets-Sheet 1 Filed July26, 1951 Nov. 3, 1953 F. M. EVAN S LIQUID FUEL PUMP 2 Sheets-Sheet 2Filed July 26, 1951 Fig.3

I NS 1.14 7 h. IN

Patented Nov. 3, 1953 LIQUID FUEL PUMP Fraser Mackie Evans, Acton,London, England, assignor to C. A. V. Limited, Acton, London,

England Application July 26, 1951, Serial No. 238,631

Claims priority, application Great Britain August 16, 1950 6 Claims.

This invention relates to variable-delivery liquid fuel injection pumpsfor internal combustion engines, of the kind in which a reciprocatoryplunger (or each of a plurality of such plungers) has mounted on it aslidably adjustable sleeve for controlling a spill passage in theplunger. The object of the invention is to enable the rate of output ofsuch a pump to be automatically controlled in a simple manner.

According to the invention there is provided in a pump of the kind abovespecified, a control means comprising the combination of a spillchamber, a sleeve adapted to control communication between the spillpassage in the plunger and the spill chamber, a throttle adapted tocontrol a discharge passage from the spill chamber, a stop whichdetermines the normal position of the sleeve, and a spring adapted tomove the sleeve towards the stop, the liquid pressure in the spillchamber being utilised for moving the sleeve away from the saidposition.

In the accompanying drawings:

Figures 1, 2, 3 and 4 are sectional views illustrating diagrammaticallyfour typical embodiments of the invention.

Referring to Figure 1, there is formed in the body a of the pump, a boreb in which is slidable the plunger c. The discharge stroke of theplunger is effected by a rotary cam d acting on a slipper e whichsupports one end of the plunger, the suction stroke being effected by aspring I.

The working chamber of the pump is supplied from the fuel inlet itthrough an annular chamber 12 and ports At the discharge end of thechamber g is arranged a delivery valve 70 loaded .by a spring m. Fueldischarged past the valve f .is delivered through the outlet 11..

In the body part a is formed a spill chamber 0, and adjacent to thischamber is formed a subchamber p, the two chambers being separated by anannular land q through which extends the sleeve 1- which is slidable onthe plunger. The sleeve has formed on it a collar s which abuts againstone end of the sub-chamber under the action of a spring t contained inthe sub-chamber. The end of the sub-chamber against which the collar sabuts serves as a stop for determining the normal position of the sleever.

In the plunger 0 is formed the spill passage u leading from the workingchamber of the pump 2 by way of radial ports '0 to an annular'groove won the plunger, which groove is controlled by the sleeve. If desired anon-return valve :1: may be provided in the plunger, as shown, orelsewhere between the working chamber 9 and the subchamber p.

The drawing shows the plunger at the commencement of its deliverystroke. The first effect of the plunger during this stroke is to out oithe ports 7'. Later the fluid is discharged through the valve It. Whenthe plunger approaches the end of this stroke, the groove w on theplunger passes out of the sleeve, and so allows fuel to escape to thespill chamber, so preventing further discharge through the valve k.

To enable the pump output to be automatically controlled, the spillchamber is provided with an outlet passage y leading to a passage .2which communicates with the inlet chamber 2', and for controlling therate of fiow through the passage y there is provided a throttle 2. Inthe example shown the throttle is adjustable by a lever which isoperable manually or automatically. 0r alternatively provision may bemade for adjusting the spring t. The sub-chamber p may also be arrangedin communication with the passage 2.

The arrangement is such that so long as the output of the pump does notexceed a predetermined rate, then for a given setting of the throttle,the fuel entering the spill chamber will pass out to the passage 2 at arate which will allow the spring t to hold the sleeve r in its normalposition as shown in the drawing. But if the rate of pump output exceedsthe predetermined amount, liquid fuel pressure will build up in thespill chamber sufficient to move the sleeve against the action of thespring t and so allow the liquid fuel to escape into the spill chamberat a correspondingly earlier period in the discharge stroke of theplunger, the extent of movement of the sleeve being dependent (for agiven setting of the throttle) on the rate of output of the pump.Consequently, so long as the rate of actuation of the pump remainsnormal, the sleeve will remain in its normal position but when the saidrate of actuation is exceeded, the sleeve will move and reduce the rateof fuel output from the pump.

' The normal setting can be varied by appropriate is essentially thesame as that shown in Figure 1, but differs in the following details.

At one side of the spill chamber there is formed in the body part a ofthe pump, a cylindrical chamber 3 which contains a piston 4 loaded by aspring 5. The piston 4 is connected to the sleeve 1 by a bell-cranklever 6. The extent of movement of the piston 4 under the action of thespring 5 is limited by a projection 1 on the piston which can abutagainst the adjacent wall of the spill chamber, which wall serves as astop. The spill chamber is provided with an outlet passage :1 which iscontrolled by the throttle 2. This throttle may be adjustable as shown,or alternatively the spring 5 may be adjustable. As in the arrangementshown Figure l, the pas-- sage y opens into a passage z'Iea-ding to theinlet chamber 2'. Also the chamber 3 is in communication with thepassage 2.

The normal position of the. sleeve 1 is that shown in the drawing, andthe sleeve remains in this position so long as a normal pressure existsin the spill chamber. But in the event of the rate of output of the pumpexceeding a predetermined-amount, the pressure in the spill chamberincreases'and-byits action on the piston 4, causes the latter to-movethe sleeve r in the direction for allowing. fuel to escape from theworking chamber of the pump at an earlier instant. during the deliverystroke of the plunger 0.

In the examples illustrated by Figures 1 and 2, only the'plu-nger c isshown. But it will be understood that two or more plungers may beprovided, each having associated with it-a controlling sleeve 1',spillchambero, and-throttle 2 as above described.

Figure 3 illustrates an application of the .in-

- vention-to a pump'of the kind in which the reciprocatory motion of asingle plunger serves to effiectthe pumping action, and which rotarymotion of the plunger" about its longitudinal axis serves "to distributesuccessive discharges to each in turn of aplurality'of engineeylinders.the

example shown, reciprocation of the plunger is. eflected .by'thealternate ,actions of a rotary cam 9 on a lever t0, and 1a spring.Rotary motion isimparted to theplunger through helical gear wheels 12.Liquid .fuel is supplied: at-. the inlet 11., from which it passesthrough the chamber 2' tothe ports aqleading to-the working chamber g ofthe pump. During the deliveryp-strokepf the plunger 0 thealiquidpasses.down the axial boreu to a radial port ,t3zand thence, by way-:ofalongitudinal groove [4 in-theplun-ger to each in turn of thev'outletpassages-15 (of which two are shown in the drawing).

The application ofthe {present invention $015136 pump shown in Figure 3iszessentially'similar to that shown in Figure 1, corresponding Partsbeing identified by the same reference :letters.

Figure 4 illustrates the application of the ,inventionin a modifiedformtoa pumpo-f the kind shown in Figure 3. In this modification, .theplunger 0 has formed on it. a coaxial. extension 16, and the workingchamber -g of. thepump is of annular form.. Liquid fuel is admitted tothe working chamber from .an inleth through-acyli-ndrical-chamber t1,passages 18 and ports t9, and liquid can passfrom the-working chamber tothe-bore u throughayradial port 26, vthebo-re it being closed at itsupper end. On the plunger ;a ;.pist,on ;;2.. In. this..exarnplerthe-spillchamber o is formed by the upper portion of thechamber 4 l1, and the sleeve 1' is held in its normal position againstan adjustable stop 2| by the spring t. The spill chamber is providedwith an outlet 1/ which is controlled by a throttle 2 and which opensinto a passage 2 leading to the inlet chamber IT. The action of thesleeve r is essentially similar to that already described. When theplunger 0 approaches the end of its discharge stroke, the annular groovew on the plunger extension IG (which communicates with the axial bore wthrough ports Incomes opposite the passage 22 in the sleeve and allowsliquid to escape trom the working chamber 9 to the spill chamber 0, Solong as the rate of output of the pump remains below the amountdetermined by the throttle the sleeve-remains in its normal position,but when the rate is exceeded, the liquid pressure in the spill chambermoves the sleeve inoppositionto the spring t for effecting earlierdischarge from the working chamber to the spill chamber.

As already mentioned, the sleeve in the example shown in Figure 4 isclosed at one end, thus forming a chamber 24 between one end of theplunger extension and the closed end of the sleeve. This chamberis inpermanentcommunication with the inlet chamber 1.! by way of a passage.25.

By this invention, automatic restrictionof the r f utput of pum c h inddes be to anvdesired am untecan-b f ct d a e y simpleand convenientmanner.

Having thus described my invention what I ciaim as new and desiretosecurev by- Letters: Patout is:

1. In a variable-delivery liquid fuel injection pump-for an internalcombustion engine, of the kind having a reciproeatory plunger meansslidable in a bore, the combination comprising a spill chambersurrounding the plunger means, passage meansada-pted to affordcommunication between the eliecti-ve end of the plunger means and-thespill chamber, a sleeve surrounding the plunger means for controllingcommunication between the saidpassage-means and-the-spill chamber, adischarge-passage 'com-rminicating with the spill chamber,throttle-meansinsaid discharge passage for restricting -fiow therein, stop means fordetermining the position of the sleeve'to afford normal-pump output bypermitting spill to occur'towards the end of the. plunger stroke, springmeans for urging the sleeve towards the said step means, and pistonmeans operatively associated with the sleeve and exposed ,to the liquidpressure afforded in the spill chamber .by

thea-ioresa-i'd throttle means whereby the sleeve will be moved awayfrom "thestopv means and thereby reduce-the effective stroke-10f: theplunger when said-pressure overcomes the force otthe spring means.

2. A fuel pump accordingfto claim. 1, comprising a sub-chamberassociated with :thespill chamber, the sleeve bei ng slidably' mounted..on the plunger at apositidrrbetweerr thespillchamher and thesub-chamber, 'one'end of the sleeve being exposed' to pressure liquid inthe spill chamber and the other end having a formation adapted toco-operate with a part of the subchamber wall which constitutes the stopmeans.

'3. A fuel pum paccording to claim I, in which the sleeve is slid'ableon apart of the plunger extending. through the spill chamber andcomprising a. spri'ng loade'd piston arranged to be subject to theliquid" pressure in" the spill chamher, an operative connection betweensaid piston and the sleeve, and stop means engageable by the piston fordetermining the normal position of the sleeve.

4. A fuel pump according to claim 1, in which the plunger receives bothreciprocatory and rotary movements, the rotary movement serving todistribute successive charges to a plurality of engine cylinders.

5. A fuel pump according to claim 1, in which the plunger receives bothreciprocatory and rotary movements, the rotary movement serving todistribute successive charges to a plurality of engine cylinders, and inwhich the sleeve is associated with an extension of the plunger.

6. A fuel pump according to claim 1, in which the throttle means isadjustable.

FRASER MACKIE EVANS.

References Cited in the file of this patent UNITED STATES PATENTS 10Number Name Date 2,187,151 Gillen Jan. 16, 1940 2,393,544 Lum Jan. 22,1946 2,517,483 Haut et al Aug. 1, 1950

